val get_dims : Sdlvideo.surface -> int * int
val sdl_init : unit -> unit
val compare_colors : int * int * int -> int * int * int -> int
val compare_pixels : Sdlvideo.surface -> int * int -> int * int -> int
val insert : ('a -> 'a -> bool) -> ('b -> 'a) -> 'b -> 'b list -> 'b list
val compare_grey : 'a * 'b * 'c -> 'a * 'd * 'e -> bool
val level : int * int * int -> float
val color2grey : int * int * int -> int * int * int
val median_filter : Sdlvideo.surface -> int -> Sdlvideo.surface -> unit
val cut : Sdlvideo.surface -> Sdlvideo.surface -> Sdlvideo.color list
val sample : Sdlvideo.surface -> int -> Sdlvideo.surface -> unit
val process_image : string -> Sdlvideo.color list ref -> string
val sample_image : string -> int -> string
val filter_image : string -> int -> string
